Loop through dates by month in bash

date-loop.sh

#!/bin/bash

start_date=2019-10-01
end_date=2019-10-31

while [ "$start_date" != 2017-10-01 ]
do
  echo $start_date $end_date
  start_date=$(gdate -I -d "$start_date - 1 month")
  end_date=$(gdate -I -d "$start_date + 1 month - 1 day")

done